Multiple Sprocket Assembly for a Bicycle

ABSTRACT

A roller chain based drive train for a bicycle includes a sprocket assembly configured for mounting to a hub of a rear wheel of the bicycle. The sprocket assembly includes a smaller sprocket, a larger sprocket, and a plurality of pins connecting the smaller sprocket and the larger sprocket to each other. The pins are mounted in outer pin mount holes on the smaller sprocket and in the inner pin mount holes on the larger sprocket.

This application claims priority to, and/or the benefit of, U.S. patentapplication Ser. No. 12/939,989, filed Nov. 4, 2010, priority to, and/orthe benefit of, German patent application DE 102009051928.9, filed onNov. 4, 2009, and German patent application DE 102010027228.0, filed onJul. 15, 2010.

BACKGROUND OF THE INVENTION

The present invention relates to multiple sprocket assemblies forbicycles, and more particularly, to a multiple sprocket assemblyincluding a smaller sprocket and a larger sprocket connected by pins.

A multiple sprocket assembly mounted to a rear wheel is one of the maincomponents of a drive train for mountain and racing bikes. Multiplesprocket assemblies may include as many as eleven sprockets. Thesprockets are highly loaded components and thus are subject to wear.Conventional sprockets have an inner contour with a torque-transmittingprofile that is mountable to a driver of a cassette hub or to an outerring of a freewheel hub. The spacing between adjacent sprockets iscritical for shifting the bicycle chain from one sprocket to theadjacent sprocket and is determined by how the torque-transmittingprofile on the sprockets engage the driver or the outer ring of thefreewheel hub. The sprockets are also subject to an undesirable bendingload as a result of oblique chain tensile forces.

One development trend in multiple sprocket assemblies is weightreduction. This objective may be achieved, while still satisfying thementioned basic requirements, by support elements such as spidersdisposed between the sprockets and the driver. However, the achievedweight reduction is then limited.

To reduce lateral bending of individual sprockets, pins may be used tosupport the sprockets relative to each other. For example, the documentJP 59-165293 discloses the use of such pins on a freewheel hub anddocuments, DE 10 2007 010 456 and DE 10 2007 006 852 disclose use ofsuch pins on a cassette hub. Further, document DE 102 60 565 discloses amultiple sprocket assembly having a spider with a third sprocket rivetedto the largest sprocket, in addition to the two sprockets.

The document EP 2 045 181 discloses a multiple sprocket assemblyincluding individual sprockets radially supported on a driver andconnected to each other by a spacer element. The individual sprocketsare fastened to the spacer element. The connecting holes on theindividual sprockets are determined by connecting holes on the spacerelement.

Another approach to minimize weight is disclosed in document DE 10 2008010 904. The individual sprockets are formed as one piece from a singleblank by turning and milling operations. This involves a gradation ofnumber of teeth with larger differences in the number of teeth, as itgiven priority during use for a mountain bike. The support structure ofthe sprocket assembly forms a hollow element in the shape of a cone. Thesprockets are not supported on a “spider” adapter relative to a driveron the rear wheel hub. Instead, the hollow cone element contacts and issupported on the driver at two positions axially spaced from each. Thehollow cone element includes annular support elements having an annularcylinder and an annular disc. Openings between the annular supportelements permit passage of dirt and sludge. Dirt accumulation beneaththe chain engaging on the sprocket can be avoided by these openings.Otherwise the chain would force dirt patches on the sprocket inward andcompress and consolidate them there. The consolidated dirt accumulationscan increasingly grow in the radial direction and increasingly force thechain outward until the chain no longer properly engages on the sprocketteeth and finally jumps off. Despite its very low weight, the supportstructure is sufficiently rigid and solid so that interfering largerdeformations and breaks as a result of the drive force of the chain maybe avoided.

One disadvantage of the above sprocket assembly is the high cost ofmanufacture by machining methods of turning and milling. Accordinglythere is a need for a multiple sprocket assembly having both reducedweight, satisfies the strength and rigidity requirements and is simpleand cost-effective to manufacture.

SUMMARY OF THE INVENTION

The present invention provides a multiple sprocket assembly engageablewith a roller chain and mountable to a driver of a rear wheel of abicycle. The multiple sprocket assembly includes a smaller sprocket anda larger sprocket. Each of the smaller and larger sprockets has aradially outer ring with a plurality of teeth for engaging the rollerchain. The radially outer ring has a plurality of radially outer pinmounts including a hole. The radially outer pin mounts are aligned withthe teeth. The sprockets have a plurality of radially inner pin mountsconnected to the radially outer ring forming a single piece. Theradially inner pin mounts includes a hole. The radially inner pin mountsare aligned with the plurality of outer pin mounts disposed on anadjacent smaller sprocket. A plurality of pins connects the smallersprocket and the larger sprocket to each other. The pins are mounted inthe holes in the outer pin mounts on the smaller sprocket and in theholes in the inner pin mounts of the larger sprocket. A first mountingsprocket is connected to the smaller sprocket by pins and a secondmounting sprocket is connected to the larger sprocket by pins. The firstand second mounting sprockets are supported on the hub axle at twopositions spaced apart in the axial direction of the hub axle.

In one embodiment of the present invention, the smaller and largersprockets include a radially inner ring having circumferentialconnectors extending between at least two adjacent inner pin mounts. Aradially outer edge of the hole in the outer pin mount may be disposedat a radial height of an outer base contour between adjacent teeth andan edge of the hole in the outer pin mount that is parallel to a loadflank of the tooth is spaced from the load flank by a distance equal toabout a diameter of the pin.

In one embodiment of the present invention, the radially outer ring isdirectly connected to the inner pin mount. In another embodiment, thelarger and smaller sprockets include radial connectors extending betweenthe radially outer pin mounts and the radially inner ring. One of thesmaller and larger sprockets may include a radial support radiallyabutting the driver. The multiple sprocket assembly further includes anend sprocket having a number of teeth greater than a largest sprocketand a radial support radially abutting the driver. The end sprocket hasa torque-transmitting profile engageable with the driver. The endsprocket may have an inner region, an outer region and connecting armsdisposed between the inner and outer regions. The connecting arms may besloped in the drive direction of rotation between the outer region andthe inner region. The inner region may have openings and inner armssloped from radially outward to radially inward in the drive directionof rotation.

In one embodiment of the present invention, the pins are interferencefit. Alternatively, the pins may be glued or welded to the sprockets.The pins 7 may have a support collar in their axial direction. The pinsmay include at least one beveled end. The beveled end of the pin mayprotrude beyond a face of the larger sprocket. An end of the pin on thesmaller sprocket may be flush with a face of the smaller sprocket. Thebeveled end of the pin may protrude beyond a face of the smallersprocket.

These and other features and advantages of the present invention will bemore fully understood from the following description of one or moreembodiments of the invention, taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a partial cross-sectional view taken along the axis ofrotation of a multiple sprocket assembly according to one embodiment ofthe present invention;

FIG. 2 is a partial perspective view of FIG. 1 viewed from the face of alargest sprocket without pins between the sprockets;

FIG. 3 is a partial view of the sprocket assembly of FIG. 2 showingsprockets with 28 and 32 teeth;

FIG. 4 is a partial view of the sprocket assembly of FIG. 1 showing apin connection between a smaller sprocket and a larger sprocket indetail, viewed from the face of the larger sprocket;

FIG. 5 is a front view of the smaller sprocket;

FIG. 6 is a front view of the larger sprocket;

FIG. 7 is a front view of an end sprocket of FIG. 1;

FIG. 8 is a cross-sectional view showing the pin being pressed into alarger sprocket; and

FIG. 9 is a cross-sectional view showing the smaller sprocket beingpressed onto the pin on the larger sprocket.

DETAILED DESCRIPTION

FIGS. 1-9 illustrate a multiple sprocket assembly according to oneembodiment of the present invention. The multiple sprocket assembly mayinclude a plurality of individual sprockets as shown in FIGS. 1 and 2.FIGS. 3-6, 8 and 9 show a smaller sprocket and/or a larger sprocket tomore easily illustrate their relationship. The smaller and largersprockets have substantially the same design. Sprockets can be viewed asa larger or smaller sprocket depending on the next smaller or largersprocket additionally being considered.

FIGS. 1 and 2 shows the multiple sprocket assembly 40 mounted on adriver 27 of a cassette hub in a longitudinal section along the axis ofrotation. The multiple sprocket assembly 40 includes an end sprocket 16having the largest number of teeth and having a different configurationthan the other sprockets. The entire multiple sprocket assembly issupported on radial supports 9 extending radially from a rotational axisof driver 27 and sprockets 1, 2 on the driver 27. Preferably, the radialsupports 9 are disposed on the end sprocket 16 and on the smallestsprocket. Alternatively, the radial supports 9 may be disposed on othersprockets which then the radial supports are formed as supportsprockets. The sprocket assembly in the axial direction is disposed on astop 28 of the driver 27. Pins 7 connect sprockets 1, 2. The entiresprocket assembly may also be mounted on an outer ring of a freewheelhub, which is mounted to rotate in the backward direction of rotationrelative to an inner ring of the freewheel hub and has a freewheelmechanism between outer and inner rings.

The multiple sprocket assembly also includes floating sprockets 36 whichare not supported on the driver and not mounted to adjacent sprocketssupported on the freewheel driver. The floating sprocket is supported bya first sprocket supported directly on the driver and a second sprocketmounted on the first sprocket.

Looking to FIGS. 3, 4 and 6, the smaller sprocket 1 is connected to thelarger sprocket 2 by the pins 7. The smaller and larger sprockets 1, 2include inner and outer rings 5, 3. The inner ring 5 includes inner pinmounts 11 having holes 12. The holes 12 of the inner pin mounts 11receive the pin of the next smaller sprocket. In the circumferentialdirection adjacent inner pin mounts 11 are connected by circumferentialconnectors 31. The outer ring 3 includes outer pin mounts 10 havingholes 41. The inner and outer rings 5, 3 are connected by radialconnectors 6 radially extending between the outer pin mounts 10 and theinner ring 5.

The outer ring 3, radial connectors 6 and the inner ring 5 providerigidity to sprocket to prevent ovalization or deformation of thesprocket in the radial direction. The inner ring 5 need not be closedand may also consist of individual separate segments in thecircumferential direction. The radial connector 6 may also radiallyextend from the inner pin mount 11 to the outer ring 3.

Looking to FIG. 5, the inner pin mounts 11 of a sprocket having a smalltooth difference relative to the adjacent smaller sprocket are disposedsuch that the radial connectors 6 are eliminated and the inner ring 5 isdirectly connected to the outer ring 3. The inner pin mounts 11 may beconnected to the outer pin mounts 10 or the outer ring 3.

The inner ring 5 has a substantially circular shape with a substantiallyequal ring width in the radial direction. The inner ring 5 may have apolygon shape, if the circumferential connectors 31 have a straighttrend between the inner pin mounts 11. The outer ring 5 has a band-likeshape and substantially the same width in the radial direction. Theouter contour of the band is determined by the shape of the teeth andthe inner contour of the band substantially follows the outer contour atequal spacing. A different spacing is found wherever outer pin mountsare provided on the outer ring 3 with a concentric hole 41 for receivingthe pin 7 and wherever strongly asymmetric teeth are present. Theseouter pin mounts 10 are disposed radially within teeth 4 and symmetricto the contour of the teeth 4 and are therefore integrated in the outerring 3. This allows the pins 7 to be disposed radially outward whilemaintaining sufficient material of the teeth 4. If these outer pinmounts 10 were to be arranged radially beneath tooth bases of teeth 4,they would have to be positioned farther radially inward to stillmaintain a minimum spacing at the contour of the tooth base.

It is advantageous to position the outer pin mounts 10 as far radiallyoutward as possible because a shorter lever arm of contact forces causedby a roller of the roller chain engaging the tooth is obtained. In thisway it is also made possible to convey dirt adhering to the sprockets onthe outside and on the pin 7 radially inward without collection of dirtand its consolidation by pressure forces from the roller chain. Theouter pin mounts 10 can only be placed far enough radially outward sothat the pins 7 inserted into holes 41 do not collide with the outer andinner plates of the roller chain, which laterally pass the tooth 4during engagement of the roller chain. A small radial intermediate spacebetween pin 7 and chain plate of the roller chain is provided.

Preferably, the outer pin mounts 10 are aligned with every second tooth4. However, not true when the sprocket has an odd number of teeth orwhen shifting aids are provided in the form of recesses on the teeth. Onvery small individual sprockets outer pin mounts 10 are consequentlyaligned to a larger number of teeth.

Additional sprockets can be arranged between the described smallersprocket 1 and the larger sprocket 2. If precisely one additional middlesprocket is present, this is a triple arrangement. In this triplearrangement the middle sprocket and the adjacent smallest sprocket, onthe one hand, and the largest sprocket and the adjacent middle sprocket,on the other hand, have the same ratios with reference to arrangement ofpin 7 and the conditions of connection. They are also constructed andact together just like the arrangement of the smaller sprocket 1 and thelarger sprocket 2 described above.

When a width of the band on the outer ring 3 and a width of ring on theinner ring 5 are approximately equal to the material thickness of thesprocket, a favorable compromise with respect to the lowest possibleweight and good manufacturing characteristics is reached. Favorableconditions are likewise obtained if the diameter of the pin 7corresponds to about 1 to 1.5 times the material thickness of thesprocket. The material thickness of a sprocket for a mountain bike isabout 2 millimeters and the material thickness of a sprocket for aracing bike is about 1.6 to 1.8 millimeters.

The pin mounts 10, 11 must offer the pin 7 a secure hold, which ispresent when the diameter of the pin hole is chosen at about three timesthe diameter of pin 7. A pin with a diameter of 2.5 millimeters issufficiently rigid and fracture-proof. The position of the pin 7 inouter ring 3 is symmetric to the tooth 4 such that the tooth 4 yieldselastically during engagement of the chain roller. This configurationresults in the tensile force from the chain being distributed to alarger number of teeth, which increases the maximum possible chaintensile force and reduces wear on the teeth. The hole 15 on the endsprocket 16 (see FIG. 7) arranged between two teeth 4 with outer pinmount 10 without a pin hole are suspended even more flexibly on theadjacent teeth 4 so that here the effect of distribution of chaintensile forces to several teeth no longer has an effect. In addition, adistribution of forces to several elements of the support structure isproduced on this account and therefore the individual elements of thesupport structure are even less loaded.

The pins 7 may be provided with or without support collars 34, whichoffer the pins 7 a secure support in the longitudinal direction duringassembly and use. By selecting an oversize between the diameter of thepin 7 and the inside diameter of the hole it can also be made possiblethat when the pin 7 is pressed into the hole a peripheral bulge oflimited height is produced which acts as a support collar. Finally, themultiple sprocket assembly in the assembled state can be provided withsurface coating so that the area of the pin 7 acquires a dimensionoutside the hole that also acts as a support collar 34 and prevents thepin 7 from moving in the longitudinal direction during use and preventsmovement of the individual sprockets 1, 2 toward each other in the axialdirection. In order for the sprockets not to be able to move away fromeach other in the axial direction the radially inward supportingsprockets are biased toward each other in the axial direction bycorresponding stops on the driver or on the outer ring of a bearing, onthe one hand, and an end screw (not shown).

A radial support 9 for driver 27 is provided on a smaller sprocket of agroup of sprockets radially inward on inner ring 5 in order to radiallysupport the sprocket group on one side. On the largest sprocket of thesprocket group an end sprocket 16 is mounted which radially supports thesprocket group on the other axial side. The end sprocket 16 satisfiesseveral tasks with respect to fixation of the multiple sprocket assemblyand transfer of the torque coming from the chain to the driver.

Looking to FIG. 5, the individual sprockets have shifting aids orrecesses 33 on the flat surfaces and tooth bevels 35 on the teeth. Therecesses 33 are components of a shifting lane along which the shiftingchain moves from a smaller sprocket to a larger sprocket and also duringthe reverse shifting process. The recesses 33 offer the chain linksspace, which is not provided at other positions on the sprocket.Deliberate shifting only at favorable positions is therefore executed.The tooth bevels serve not to allow the chain deflected by the chainguide of the derailleur in the axial direction to engage on thecorresponding tooth. No pin holes are provided within the recesses 33.Wherever possible, the recess is reduced so that the hole is notpositioned in the recess 33.

Looking to FIG. 2, a number of end pins 17 are disposed between thelarger sprocket 2 and the end sprocket 16. Their position is againdetermined by the position of the teeth on the larger sprocket 2, whichin the arrangement of a larger sprocket 2 and end sprocket 16 is viewedas the smaller sprocket and therefore stipulates the position of the pinmounts. Looking to FIG. 7, the end sprocket 16 includes a centralopening 18 in which the driver 27 is inserted during assembly of themultiple sprocket assembly. The opening includes a torque transmittingprofile or splines 19 to transfer torque between the end sprocket 16 anddriver as a result of the chain tensile forces K engaging on a sprocket.

The end sprocket 16 has an inner region 20, an outer region 21 andconnecting arms 22. The connecting arms 22 extend between the outerregion 21 and the inner region 20 and are aligned deviating from theradial direction in the drive direction of rotation D. Because of thisthey are acted upon by pressure and their maximum possible length isdetermined by the pressure force to be taken up by them, which must liebelow their critical buckling load. The inner region 20 can thereforehave a greater width in the radial direction. For weight reduction,openings 23 are provided so that inner arms 24 acted upon by pressureare also formed. The outer region 21 can be configured differently. Ifit is designed as a ring, it is provided with a continuous groove on theflat side of the sprocket in order to save weight and in order to bringthe rigidities of the radially outer end tooth ring 30 and the radiallyinner part of the outer region 21 provided with teeth 4 into a favorableratio.

In another embodiment of the outer region 21, two additional arms 29 areprovided between the connecting arm 22 and the end tooth ring 30. At thepoints of entry of the two additional arms 29 into the connecting arm22, holes 15 are provided to receive end pins 8. These pins 8 can have agreater diameter than the pin 7 for connection of the other larger andsmaller sprockets 1, 2 in order to offer these end pins 8 sufficienthold in the end sprocket 16, which can be made from aluminum.

The end sprocket 16 may be flat or the inner region 20 is offset in theaxial direction relative to the outer region 21 to bring the teeth 4 onthe end sprocket 16 closer to the spokes of the wheel so that greaterdesign space can be furnished for a larger number of sprockets. On theinside periphery of opening 18 the end sprocket 16 has splines 19. Thesecan protrude in the axial direction beyond the flat surfaces of the endsprocket in order to obtain optimal engagement conditions between theend sprocket and driver. The end sprocket must have sufficiently highstability against keying, i.e., against deformation of the central areain the axial direction from the plane of extent of the end sprocket 16,otherwise unduly large deformation would occur with the laterallyengaging chain forces. The described end sprockets can also be used inconjunction with a one-piece multiple sprocket arrangement according toDE 10 2008 010 904 mentioned in the introduction.

The splines 19 can also be arranged on the smaller sprocket 1,specifically as an alternative or in addition to the described splineson the end sprocket 16. However, preferably the splines are on the endsprocket 16. If the splines 19 are disposed on the end sprocket andadditionally on the smaller sprocket 1, it may happen that in theextreme case all forces are transferred from the sprockets to the driveronly through the smaller sprocket. An increased manufacturing andassembly expense would therefore occur without a gain in safety duringcontact with the driver.

If the splines 19 are disposed only on the smaller sprocket 1, localoverloads may then occur because individual radial connectors 6 andsections in the outer ring 3 or in the inner ring 5 are overloaded. Withthe splines 19 disposed only on the end sprocket 16, inner region 20 ofthe end sprocket 16 has greater stability for transfer of contact forcesto the driver. A distribution of loads to several splines is obtained.If forces introduction on the multiple sprocket assembly occur byengagement of the chain on one of the sprockets spaced from the endsprocket 16, the forces are then distributed to several components ofthe support structure and are therefore also distributed to severalconnecting arms 22. The elements of the support structure on the endsprocket 16 are also already designed more stable anyway. Overall thisleads to a more noncritical load distribution.

The pins 7 already have bevels 52 on their ends for manufacturingreasons and do not have sharp edges. If the end pins had a sharp edge, aburr may be present which would be an obstacle during pressing in of thecorresponding the pin 7 into the holes 41, 12 of the pin mounts 10, 11,respectively. Sharp-edge pin ends therefore fail. The bevels 52facilitate threading of the end of pin 7 into holes 41, 12 of the pinmounts 10, 11, respectively. On the other hand, lower overlap betweenthe outer surface of the pin 7 and the inner surface of the holes 41, 12in the pin mounts 10, 11 occurs on the sprocket 1, 2. This lower overlapreduces the quality of the sprocket-pin connection with respect to thestrength and lifetime even with the forces to be transferred by thesprocket-pin connection alternating between maximum and minimum values.

The holes 41, 12 in the sprockets 1, 2 also do not have a sharp-edge ontheir two ends. Because of the punching direction during punching out ofsprockets 1, 2, an unavoidable bevel 50 exists on one side, whichappears as a continuous inner bevel. As a result of shifting aids thatare present in a larger extent on the side of the sprocket 2 facing thenext smaller sprocket 1, a punching direction is chosen that produces onthe side facing the next larger sprocket 2 a sharp edge end 51 of hole12 and on the side facing the next smaller sprocket 1 a hole 12 with abevel 50, as shown in FIGS. 8 and 9.

To ensure proper engagement of roller chain 13 with the teeth of thesprockets during a shifting process, a precise and defined sprocketspacing d of the sprockets between the sides of sprockets 1, 2 facingthe next smaller sprockets is necessary. However, since the materialthicknesses of the individual sprockets for reasons of manufacture vary,irregularities in sprocket spacing d may occur during assembly of thesprocket assembly. If several sprockets are combined, their tolerancescan be added up. Consequently, depending on the number of sprockets, thedistance from the largest to smallest individual sprocket can deviate upto a millimeter from the target dimension as a result of sprocketthickness tolerances. This distance then does not permit properengagement of the chain on the sprocket teeth and also hampers theshifting process.

If during assembly of several individual sprockets by means of the pinsto an assembly unit the flat surface facing the next smaller sprocket isused as a reference surface, a further complication results. Thissurface is only suitable with considerable restriction as a supportsurface on an assembly device during the joining of several sprockets 1,2 by pins 7. Starting from there, shape elements are preferably arrangedthat serve as shifting aids. These give the chain changing from one toanother sprocket room to run on and run off. The more shape elements arepresent, the less contact surface remains for assembly. For this purposean assembly device must be constructed at great expense, which can beused as a matching counter piece when little support surface is presentand which withstands the high pressure loads that are exerted pointwise.

In order to get around the problem of added tolerances, the differentpossible material thicknesses m of the individual sprockets 1, 2 mustalready be balanced or compensated during assembly. This compensationcan be implemented by two simple and cost-effective method steps, bymeans of which the requirement for a complicated assembly device alsodrops out.

Looking to FIG. 8, first the pin 7 is pressed by a first tool 54 throughone end of holes 12 in the inner pin mounts 11 of inner ring 5 of thelarger sprocket 2 in axial direction A until a defined overhang u isformed on the opposite side of the sprocket 2. Preferably, the size ofthe overhang u equals the height of the bevel on the end of the pin 7.The larger sprocket 2 is supported by a first support 53.

In this process the fact is exploited that production of pins with verynarrow length tolerance is possible. In addition, this method alsoprofits from the discussed property of holes 12 which can have asharp-edge or a bevel. It has proven to be particularly advantageous topress the pins into the hole end having the bevel.

If, in the alternative embodiment, a pin 7 was only pressed through thehole 12 in the inner pin mount 11 from the side with the bevel 50 in theaxial direction A until the top of the pin were flush with the back ofthe sprocket, in which case there would be no overhang u, owing to thebevel of the pin 7 in addition to the bevel, there would be lesspressing-in or contact surface between the pin 7 and the surface of thehole 12 of the inner pin mount 11. In this case there would be a greaterrisk that a pin 7 would loosen from the hole 12 of the inner pin mount11 through the shear forces that fluctuate between maximum and minimumvalues and threaten the stability of the sprocket assembly. If, however,pin 7 is pushed out beyond the flat surface of the larger sprocket, theconnection gains strength not only via the greater overlap and contactsurface. The sharp-edge punch contour 51 of hole 12 of inner pin mount11, which is now in contact with the smooth pin 7, also ensures thelargest possible overlap on the sprocket-pin connection and goodfixation of the pin 7 in hole 12. Loosening or migration of pin 7 out ofhole 12 of inner ring 5 is suppressed with this first pressing-in stepin a simple manner in the form of force fitting over the maximumpossible length and sufficient strength of the connection from pin 7 andthe larger sprocket 2 is guaranteed. The overhang of this sprocket pinconnection therefore produces an improvement in stability and strengththat could not possibly be better because of the maximum possibleoverlap. On the side of the mentioned sprocket 2 facing the next smallersprocket 1, the pressing-in conditions cannot be further optimized,since the hole necessarily has a bevel, which already by itself means areduction in overlap.

The material thickness m has a direct effect on the sprocket spacing din addition to the distance L between the tools. When the distance Lbetween the tools for pressing-in is retained during the first assemblystep, different sprocket spacings are obtained with varying materialthicknesses.

The material thickness m can preferably be varied from one materialbatch to another, more rarely within one material batch. In order forthe same sprocket spacing d to be achieved during a change in materialthickness m, this must be controlled against by a corresponding changeon the tools in the first assembly step. The distance dimension L isthen changed.

Another advantage of the first method step with the creation of adefined overhang u is that the protrusion of pin 7 which occurs on theother side can be used as a support and contact surface for furtherpressing in the next method step.

Looking to FIG. 9, in a second step, a next smaller sprocket 1 isconnected to the larger sprocket 2 from step 1. The concentric holes 41of the outer pin mounts 10 of the outer ring 3 of the smaller sprocket 1are joined to the pins and pressed onto them by a second tool 56. Thesmaller sprocket 1 is pressed relative to the larger sprocket 2 in theaxial direction A until the ends of the pins are closed off flush withthe ends of the holes 41 in the smaller sprocket 1. As is apparent fromFIG. 9, the punch contour with bevel 50 is then situated on the axialposition of bevel 52 on pin 7. The larger sprocket 2 is supported on asecond support 55.

If, in an alternative embodiment, the pin end extended beyond the hole,no additional overlap could be gained. This position assignment of thepin end and hole therefore also generates the maximum possible overlapwith the maximum possible strength.

The pressing-in conditions on the end of hole 12 facing the next largersprocket 2 also cannot be further optimized, since the sharp-edge hole51 already has optimal overlap with the smooth pin section.

By means of these two simple method steps the sprockets can be joinedand firmly adjusted cost-effectively. The required spacing d between thesprockets 1, 2 measured from the outer surface of the larger sprocket 2to the outer surface of the next smaller sprocket 1 is maintained. Thismethod keeps the deviations minimal, an added deviation is tolerablysmall and reliable connection between pin 7 and hole 12 of the inner pinmount 11 is made possible.

In a modified form of the sprocket assembly according to the inventionit would also be possible to provide holes provided with bevels on theside allocated to the adjacent larger sprocket.

According to the described procedure, additional pins are pressed in anindividual sprocket or a preassem bled arrangement of several sprocketsand then another individual sprocket is pressed onto these pins. Itwould also be possible to press pins into an individual sprocket andthen press a preassembled arrangement of several sprockets onto thesepins. The individual sprockets into which the pins are pressed, wouldthen be the smaller sprocket.

While this invention has been described by reference to one or moreembodiments, it should be understood that numerous changes could be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to the oneor more disclosed embodiments, but that it have the full scope permittedby the language of the following claims.

What is claimed:
 1. A roller chain based drive train for a bicycle,comprising: a sprocket assembly configured for mounting to a hub of arear wheel of the bicycle comprising: a smaller sprocket having a firstradially outer ring with a first plurality of teeth for engaging theroller chain, the first radially outer ring also including a pluralityof radially outer pin mounts, each of the radially outer pin mountsincluding an outer pin mount hole having a first edge radiallypositioned at a radial height of an outer base contour between adjacentteeth of the first plurality of teeth and a second edge located near aload flank of a tooth of the adjacent teeth; a larger sprocket having asecond radially outer ring with a second plurality of teeth for engagingthe roller chain, the larger sprocket having a radially inner ringhaving a plurality of radially inner pin mounts connected to the secondradially outer ring forming a single piece, each of the radially innerpin mounts including an inner pin mount hole; a plurality of pinsconnecting the smaller sprocket and the larger sprocket to each other,the pins mounted in the outer pin mount holes on the smaller sprocketand in the inner pin mount holes on the larger sprocket; a firstmounting sprocket connected to the smaller sprocket by pins; and asecond mounting sprocket connected to the larger sprocket by pins andincluding a torque-transmitting profile engageable with a driver andcoupled to the hub, wherein torque imparted to the first plurality ofteeth of the smaller sprocket is transmitted to the hub through thetorque transmitting profile of the second mounting sprocket, the firstand second mounting sprockets radially supported on the hub at twopositions spaced apart in the axial direction of the hub.
 2. The drivetrain of claim 1, wherein the second hole edge of the outer pin mounthole is spaced from the load flank of the tooth by a distance of about adiameter of a pin of the plurality of pins mounted in the hole.
 3. Thedrive train of claim 1, wherein the radially inner ring hascircumferential connectors extending between at least two adjacent innerpin mounts.
 4. The multiple sprocket assembly of claim 3, wherein thelarger sprocket further comprises a second radially outer ring, and thesecond radially outer ring has direct connections with the inner pinmounts of the inner ring.
 5. The drive train of claim 4, wherein thesmaller sprocket further comprises a second radially inner ring having asecond plurality of radially inner pin mounts, the larger sprocket andthe smaller sprocket including radial connectors extending between theradially outer pin mounts and the respective radially inner rings. 6.The drive train of claim 1, wherein the second mounting sprocket has anumber of teeth greater than the larger sprocket.
 7. The drive train ofclaim 1, wherein the larger sprocket and the smaller sprocket do notcontact the hub or the driver.
 8. The drive train of claim 1, whereinthe plurality of pins are interference fit into a respective hole. 9.The drive train of claim 1, wherein the plurality of pins are one ofglued and welded to the sprockets.
 10. The drive train of claim 1,wherein the plurality of pins have a support collar in their axialdirection.
 11. The drive train of claim 1, wherein the second mountingsprocket has an inner region, an outer region, and connecting armsdisposed between the inner region and the outer region.
 12. The drivetrain of claim 11, wherein the connecting arms are separated byvacancies in the second mounting sprocket.
 13. The drive train of claim11, wherein the connecting arms are sloped in the drive direction ofrotation between the outer region and the inner region.
 14. The drivetrain of claim 1, wherein the pins include at least one beveled end. 15.The drive train of claim 14, wherein the beveled end of the pinprotrudes beyond a face of the larger sprocket.
 16. The drive train ofclaim 15, wherein an end of the pin on the smaller sprocket is flushwith a face of the smaller sprocket.
 17. The drive train of claim 16,wherein the beveled end of the pin protrudes beyond a face of thesmaller sprocket.